This invention relates generally to a collection mode lens system, and more particularly to an optical system including a large area detector, a collecting lens and a small lens in which the field of view is determined by the acceptance angle or numerical aperture of the collecting lens, and the diameter of the small lens, and no pinhole is used in front of the detector.
Micromachining techniques have enabled the fabrication of lenses with diameters comparable to the wavelength of light. Microlenses which are many wavelengths in diameter are used for collimation of fiber optics, wave-front sensing, and fill-factor improvement in detectors. Microlenses are also used for high spatial resolution solid immersion microscopy, where light is focused through a lens with a high index of refraction held close to the sample surface. Spherical aberration in a lens is inversely proportional to radius of curvature, making microlenses more tolerant to wave-front errors than large lenses.
As the diameter of a microlens is reduced, the ability of the lens to focus and collect light is affected. In a spherical lens, the field of view from which light is collected decreases with lens diameter. Microfabricated lenses with small fields of view can be used to direct beams of light by refracting off-axis rays. Small movements of a microlens in front of an optical fiber have been used for beam steering, optical interconnection and optical switching.
One is often interested in visualizing a small region on a sample. This is usually accomplished by a confocal arrangement using a lens with a pinhole in front of the detector. If the pinhole is small, the size of the region on the sample which is visualized is given by the diffraction limit of the objective lens combination.
The present invention is directed to a lens construction including a collecting lens and small or micro lens for collecting energy from a region of a sample in which the size of the region from which energy is collected is determined mainly by the size of the small or micro lens and the acceptance angle or numerical aperture of the collecting lens.